Cooling fins of radiation shielding material on containers for transporting radioactive material

ABSTRACT

A container for transporting decay-heat-producing radioactive material has a body which incorporates shielding material, and on said body external fins which also incorporate shielding material, the fins being inclined in at least one direction to the normal from the external surface of the container body so as to present to radiation emitted from said radioactive material on elongated attenuation path, thereby enabling the body of the container to be reduced in thickness and therefore in weight, for an equivalent shielding duty.

United Sti :ataaagaae Sidebotham et COOLING FINS OF RADIATION SI-IIELDING MATERIAL ON CONTAINERS FOR TRANSPORTING RADIOACTIVE MATERIAL Inventors: Ernest WilliamSidebotham, Eccles,

Manchester; Alan Jackson, Kenyon, both of England Assignee: United Kingdom Atomic Energy Authority, London, England Filed: June 5, 1969 Appl. N6; 830,610

Foreign Application Priority Data Feb. 8, 1968 Great Britain 32576/68 Ufs. c1. .Q 250/506, 250/515 Int. Cl. G2lf 3/00 Field of Search 250/108 ws, 106 R, 506,

References Cited UNITED STATES PATENTS 2/1964 Held et al 250/108 R Primary ExaminerArchie R. Borchelt Attorney, Agent, or Firm-Larson, Taylor and Hinds [57] ABSTRACT A container for transporting decay-heat-producing radioactive material has a body which incorporates shielding material, and on said body external fins which also incorporate shielding material, the fins being inclined in at least one direction to the normal from the external surface of the container body so as to present to radiation emitted from said radioactive material on elongated attenuation path, thereby enabling the body of the containerto be reduced in thickness and therefore in weight, for an equivalent shielding duty.

4 Claims, 1 Drawing Figure This invention relates to containers for transporting radioactive material.

Containers for transporting irradiated fuel have in the past had to be designed to compromise between the necessity to keep radiation below the limit allowed by transport regulations and the necessity to keep the weight of the container as low as is, reasonable from both the tariff and the cost of production points of view. Such design has been further complicated by the additional necessity of having to provide fins on the outsides of the containers in order that decay heat can be dissipated.

Hitherto, the heat-dissipating fins have been straight circumferential and disposed perpendicularly to the container body. Thus the material employed for the fins has contributed only locally towards the shielding function of the containers themselves.

According to the present invention, a container for transporting decay-heat-producing radioactive material, having a body incorporating shielding material and on said body external fins for dissipation of such decay heat, is characterised in that the fins incorporate shielding material and are inclined in at least one direction to the normal from the external surface of the body of said container in such a manner that radiation emitted from the radioactive material is presented with 'a total attenuation path sufficient to attenuate such radiation by a required amount, whereas emitted radiation passing normally through the body of said container in the absence of said fins would be attenuated less than said required amount.

Reference to a required amount in relation to attenuation of radiation is to be understood to relate to a limit on the amount of radiation emitted from a transport container as set by international, national or local regulations, codes of practice or recommendations governing the transport of radioactive material.

ln'one convenient form, the fins are inclined in two directions to said normal and are sufficiently closely spaced so that emitted radiation in addition to having to pass through the body of the container has additionally to pass through at least two thicknesses of the fin material. a

' In a preferred form, the fins are circumferential and each fin in cross-section has two integral limbs at right angles to one another, one limb of each fin being secured along its free edge to the external surface of the container body so as to be at substantially 45 thereto,

The body 1 of the container has semi-circular fins 2 circumferentially welded thereto at 3, thefins 2 being formed from angle iron (for example: 4 X 4 X 4 inch, or 4 X 6 X /8 inch the longer limb in the latter example being the non-welded limb, which improves overlap where close pitching is employed) and secured to the container body 1 with the limbs thereof at to the normal from the body 1. Each two semi-circular fin portions are butt-welded at their ends to form a complete circumferential fin 2. The drawing also shows non-radiused fins (the three on the left hand side) and one fin (the one on the extreme left hand side) with a longer free limb than the remainder, as examples of alternatives which can be employed exclusively or in combination.

The gap between the fins 2 is not significantly more than twice the limb thickness, so that any radiation passing through the container body 1 and not having.

been completely absorbed by the thickness of the wall of the body 1 has to meet at least two thicknesses of the limbs of the fins 2 to be absorbed or sufficiently attenuated thereby. I

A container according to the invention is advantageous in that the wall thickness of the container body, compared with that of the known construction herein before referred to, can be reduced, for the same shielding requirement (for example by 2.8 X limb thickness), which leads to a saving in both weight and cost. Furthermore, improvement in its performance in drop tests is to be expected.

The invention envisages shapes and fabrications of fins other than according to the describedexample, together with the employment of the described or other fins on plane-sided or other-than-cylindrical containers.

We claim:

1. For transporting decay-heat-producing radioactive material, a container comprising a body which incorporates radiation shielding material and external cooling fins on said body, said fins incorporating radiation shielding material and being inclined in at least one direction to the normal from the external surface of said and the spacing between fins being substantially twice 7 the limb thickness. This preferred form has the fins secured to the container body by welding, the fins being formed in semi-circles and produced by hot-rolling angle iron in amanner such that the limbs are at substantially 45 to'the plane of the semi-circle. To improve the flow of air over the fins for cooling purposes, it is desirable to remove material from the sharp outside corner of the right angle to leave a smooth radiused profile.

The single FIGURE of the accompanying drawing is a fragmentary side view inmedial section and illustrates a short length of a complete hollow cylindrical transport container for irradiated nuclear reactor fuel elements. i 1

body, said fins being positioned relative to each other and the degree of inclination being such that radiation emitted from the radioactive material in the direction normal to the external surface of said body is presented with a total attenuation path which includes said body and at least one of said fins, whilst radiation in a direction oblique to the external surface of said body is presented with at least an extended attenuation path afforded by oblique passage through the body, and which attenuates such radiation by a required amount,

whereas emitted radiation passingnormally through the 'body of said container in the absence of said in clined fins would be attenuated less than said required amount.

2. For transporting decay-heat-producing radioactive material, a container comprising a body which incorporates radiation shielding material, andexternal fins on said body, said fins incorporating radiation shielding material, being inclined in two directions to the normal from the external surface of said body, and said fins being sufficiently'closely spaced so that any radiation emitted from the radioactive material in addition to having to pass through the body of the container. has additionally to pass through at least two thicknesses of the fin material, whereas emitted radiation passing normally through the body of said container in the absence of said fins would be attenuated less than said required 1 I amount. 3. For transporting decay-heat-producing radioactive the spacing between fins being substantially twice the limb thickness so that any radiation emitted from the *gfradioactive material is presented with a total attenuation path which includes said and at least one of said fins and which attenuates such radiation by a required amount, whereas emitted radiation passing normally through the body of said container in the absence of said fins would be attenuated less than said required amount.

4. A container according to claim 3 wherein the external edges of said fins are radiused. 

1. For transporting decay-heat-producing radioactive material, a container comprising a body which incorporates radiation shielding material and external cooling fins on said body, said fins incorporating radiation shielding material and being inclined in at least one direction to the normal from the external surface of said body, said fins being positioned relative to each other and the degree of inclination being such that radiation emitted from the radioactive material in the direction normal to the external surface of said body is presented with a total attenuation path which includes said body and at least one of said fins, whilst radiation in a direction oblique to the external surface of said body is presented with at least an extended attenuation path afforded by oblique passage through the body, and which attenuates such radiation by a required amount, whereas emitted radiation passing normally through the body of said container in the absence of said inclined fins would be attenuated less than said required amount.
 2. For transporting decay-heat-producing radioactive material, a container comprising a body which incorporates radiation shielding material, and external fins on said body, said fins incorporating radiation shielding material, being inclined in two directions to the normal from the external surface of said body, and said fins being sufficiently closely spaced so that any radiation emitted from the radioactive material in addition to having to pass through the body of the container has additionally to pass through at least two thicknesses of the fin material, whereas emitted radiation passing normally through the body of said container in the absence of said fins woulD be attenuated less than said required amount.
 3. For transporting decay-heat-producing radioactive material, a hollow cylindrical container comprising a body which incorporates radiation shielding material, and external circumferential fins on said body, said fins incorporating radiation shielding material and each fin in cross-section having two integral limbs at right angles to one another, one limb of each fin being secured along its free edge circumferentially to the external surface of said body so as to be substantially 45* thereto, the spacing between fins being substantially twice the limb thickness so that any radiation emitted from the radioactive material is presented with a total attenuation path which includes said and at least one of said fins and which attenuates such radiation by a required amount, whereas emitted radiation passing normally through the body of said container in the absence of said fins would be attenuated less than said required amount.
 4. A container according to claim 3 wherein the external edges of said fins are radiused. 